<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型-单方向边框线</title>
    <style>
      div{
        width: 200px;
        height: 200px;
        background-color: pink;
        /* 上  实线*/
        border-top: 1px solid black;
        /* 下  虚线*/
       border-bottom: 1px dashed black;
       /* 右 */
         border-right: 1px solid black;
         /* 左 */
         border-left: 1px solid black;
      }
    </style>
</head>
<body>
    <div>div 标签</div>
</body>
</html>